An electrophotographic printer known in the art has developing devices detachably mounted therein. Each developing device includes a developing frame, a developing roller supported in the developing frame for carrying toner, and a blade assembly for restricting the thickness of the toner layer carried on the developing roller.
One such developing device that has been proposed is a developer cartridge in which the developing frame is configured of a lower frame for rotatably supporting the developing roller, and an upper frame welded to the lower frame.
In this developer cartridge, an opening exposing the developing roller is defined by the front end of a beam-like part constituting the upper frame, and the front ends of the two side walls and the bottom wall of the lower frame. The blade assembly is fixed to both the upper frame and the lower frame. Specifically, the blade assembly is fixed to screw-mounting holes adjacent to the front end of the beam-like part constituting the upper frame and to the upper front end of both side walls constituting the lower frame.